Empty menu should not show in sitemap

I run into a problem w/ i18n.
Because name of the menus created by admin (like Primary links) cannot be translated. Only their original name will show up in the sitemap.

Therefore it was impossible to filter the sitemap by language for the menus.

Solution: (I needed this patch to solve this problem in a simple way as described below)
I created a menu 'Primary links' and another menu 'Tranlated Primary Links'. Inside this menus, the menu items can be assigned to a language. (Therefore the menu items are filtered correctly when viewing the sitemap page).
But when i check both of this menus on the sitemap settings page, both of their name ('Primary links' And 'Tranlated Primary links') will show up. Although, viewing the English sitemap, the 'Tranlated Primary links' will be empty ('cause its menu items are all filtered out).
With this patch, now it is possible to make translation correctly, and IMO empty menus will not be missing for others who are not using i18n.